The present invention relates to sewing machines that form stitching patterns on a fabric web by the cooperative motion of needles and shuttles.
A sewing machine such as a quilting machine has a needle plate and a plurality of needles, which are arranged above the needle plate. The needles are reciprocated vertically to pierce a fabric web and feed upper threads. A shuttle is arranged in correspondence with each needle below the needle plate. Each shuttle is reciprocated transversely relative to the associated needle. A bobbin wound with a lower thread is housed in each shuttle. The cooperative reciprocation of the needles and the shuttles forms stitching patterns on the fabric web with the upper and lower threads.
In a typical quilting machine, a lower thread having a predetermined length is wound on a bobbin. When all of the lower thread becomes used during the sewing operation, the shuttle accommodating the empty bobbin is manually removed from its sewing position and replaced with a shuttle accommodating a full bobbin. The burdensome replacement of the shuttles degrades the sewing efficiency.
The manual replacement of shuttles is especially inefficient when using a quilting machine that employs a large number of shuttles. The manual replacement of shuttles in a quilting machine consumes a large amount of time.